U.S. patent application number 16/314767 was filed with the patent office on 2019-05-23 for alkaline dry battery.
This patent application is currently assigned to Panasonic Intellectual Property Management Co., Ltd.. The applicant listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to Satoshi Fujiyoshi, Yasufumi Takahashi.
Application Number | 20190157662 16/314767 |
Document ID | / |
Family ID | 61831718 |
Filed Date | 2019-05-23 |
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United States Patent
Application |
20190157662 |
Kind Code |
A1 |
Takahashi; Yasufumi ; et
al. |
May 23, 2019 |
ALKALINE DRY BATTERY
Abstract
An alkaline dry battery includes a positive electrode, a gel
negative electrode, a separator disposed between the positive
electrode and the negative electrode, and an alkaline electrolyte
solution contained in the positive electrode, the negative
electrode, and the separator. The negative electrode contains a
negative electrode active material containing zinc and particulate
terephthalic acid. The terephthalic acid contained in the negative
electrode has an average particle diameter of 25 to 210 .mu.m.
Inventors: |
Takahashi; Yasufumi; (Hyogo,
JP) ; Fujiyoshi; Satoshi; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
Panasonic Intellectual Property
Management Co., Ltd.
Osaka-shi, Osaka
JP
|
Family ID: |
61831718 |
Appl. No.: |
16/314767 |
Filed: |
July 18, 2017 |
PCT Filed: |
July 18, 2017 |
PCT NO: |
PCT/JP2017/025862 |
371 Date: |
January 2, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 6/06 20130101; H01M
6/04 20130101; H01M 4/628 20130101; H01M 2004/023 20130101; H01M
4/24 20130101; H01M 4/244 20130101; H01M 4/62 20130101; H01M 2/16
20130101; H01M 4/42 20130101 |
International
Class: |
H01M 4/24 20060101
H01M004/24; H01M 4/62 20060101 H01M004/62; H01M 4/42 20060101
H01M004/42; H01M 6/04 20060101 H01M006/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 3, 2016 |
JP |
2016-196038 |
Claims
1. An alkaline dry battery comprising: a positive electrode; a gel
negative electrode; a separator disposed between the positive
electrode and the negative electrode; and an alkaline electrolyte
solution contained in the positive electrode, the negative
electrode, and the separator, wherein the negative electrode
contains a negative electrode active material containing zinc and
particulate terephthalic acid, and the terephthalic acid has an
average particle diameter of 25 to 210 .mu.m.
2. The alkaline dry battery according to claim 1, wherein an amount
of the terephthalic acid in the negative electrode is 0.01 to 0.5
parts by mass relative to 100 parts by mass of the negative
electrode active material.
3. The alkaline dry battery according to claim 1, wherein the
terephthalic acid has an average particle diameter of 100 to 210
.mu.m.
4. The alkaline dry battery according to claim 1, wherein the
separator contains 50 to 70 mass % of polyvinyl alcohol.
5. The alkaline dry battery according to claim 1, wherein the
negative electrode contains 0.1 to 1.0 parts by mass of a potassium
halide relative to 100 parts by mass of the negative electrode
active material.
Description
TECHNICAL FIELD
[0001] The present invention relates to an alkaline dry battery
including a gel negative electrode.
BACKGROUND ART
[0002] Compared to manganese dry batteries, alkaline dry batteries
(alkaline-manganese dry batteries) have high capacity, output high
current, and are thus widely used. An alkaline dry battery includes
a positive electrode, a gel negative electrode, a separator
disposed between the positive electrode and the negative electrode,
and an alkaline electrolyte solution contained in the positive
electrode, the negative electrode, and the separator. The negative
electrode contains a negative electrode active material containing
zinc. Such an alkaline dry battery has been variously studied.
[0003] For example, it is proposed that terephthalic acid be added
to the negative electrode as an anti-corrosion agent for the
negative electrode active material (see PTL 1). For terephthalic
acid to exhibit an anti-corrosion agent effect, the surface of the
negative electrode active material needs to be covered by very
small terephthalic acid particles (e.g., particle diameter is 2
.mu.m or less).
CITATION LIST
Patent Literature
[0004] PTL 1: Japanese Published Unexamined Patent Application No.
2-194103
SUMMARY OF INVENTION
[0005] In an alkaline dry battery including a gel negative
electrode, in the case where the battery is subjected to a great
impact or vibration when dropped or while being transported, the
gel negative electrode may flow to (be scattered onto) the positive
electrode and cause an internal short circuit, and the battery may
generate heat. In particular, in an alkaline dry battery having an
inside-out structure including a hollow cylindrical positive
electrode and a gel negative electrode disposed in the hollow
portion of the positive electrode, buckling of the separator may
occur with flowing (scattering) of the negative electrode, and
thus, the negative electrode is likely to leak to the positive
electrode.
[0006] Because electronic devices in which an alkaline dry battery
is used as a power source have high performance, alkaline dry
batteries are desired to achieve higher capacity and higher
output.
[0007] An object of the present disclosure is to achieve higher
capacity and higher output of an alkaline dry battery including a
gel negative electrode, to prevent or reduce an occurrence of an
internal short circuit caused by flowing of the negative electrode
to the positive electrode, and to prevent or reduce heat generation
in the battery that occurs with the internal short circuit.
[0008] One aspect of the present disclosure relates to an alkaline
dry battery including a positive electrode, a gel negative
electrode, a separator disposed between the positive electrode and
the negative electrode, and an alkaline electrolyte solution
contained in the positive electrode, the negative electrode, and
the separator. The negative electrode contains a negative electrode
active material containing zinc and particulate terephthalic acid.
The terephthalic acid has an average particle diameter of 25 to 210
.mu.m.
[0009] According to the present disclosure, higher capacity and
higher output of an alkaline dry battery including a gel negative
electrode are achieved, and an occurrence of an internal short
circuit caused by flowing of the negative electrode to the positive
electrode and heat generation in the battery that occurs with the
internal short circuit are prevented or reduced.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a front view of an alkaline dry battery according
to an embodiment of the present invention, with a part of the view
of a cross section of the battery.
DESCRIPTION OF EMBODIMENTS
[0011] An alkaline dry battery according to an embodiment of the
present invention includes a positive electrode, a gel negative
electrode, a separator disposed between the positive electrode and
the negative electrode, and an alkaline electrolyte solution
contained in the positive electrode, the negative electrode, and
the separator. The negative electrode contains a negative electrode
active material containing zinc.
[0012] The negative electrode contains particulate terephthalic
acid (para isomer). Unlike phthalic acid (ortho isomer) and
isophthalic acid (meta isomer), terephthalic acid is unlikely to
dissolve in the gel negative electrode. When the negative electrode
contains particulate terephthalic acid, the surface of terephthalic
acid particles dissolves slightly, and most of the particles remain
without dissolving in the negative electrode. Thus, when the
negative electrode contains particulate terephthalic acid, the
negative electrode is whitely turbid. Such a phenomenon is not seen
when the negative electrode contains phthalic acid or isophthalic
acid.
[0013] When the terephthalic acid in the negative electrode has an
average particle diameter of 25 to 210 .mu.m, the negative
electrode has appropriate viscosity and elasticity. Thus, even if
the battery is subjected to a great impact or vibration when
dropped or while being transported, flowing (scattering) of the
negative electrode to the positive electrode is sufficiently
prevented or reduced. As a result, the occurrence of an internal
short circuit and heat generation in the battery that occurs with
the internal short circuit are prevented. In an alkaline dry
battery having an inside-out structure, buckling of the separator
that occurs with flowing (scattering) of the negative electrode is
prevented or reduced, and thus, leakage of the negative electrode
to the positive electrode is sufficiently prevented or reduced.
[0014] The above white turbidity of the negative electrode and an
effect of preventing or reducing flowing of the negative electrode
are unlikely to be seen when the terephthalic acid in the negative
electrode has an average particle diameter of 20 .mu.m or less.
[0015] When the terephthalic acid in the negative electrode has an
average particle diameter of 25 to 210 .mu.m, discharge performance
is improved. In particular, high-rate discharge performance is
improved, and higher capacity and higher output are achieved.
Terephthalic acid having the above specific average particle
diameter is a good dispersant in the gel negative electrode. In
other words, dispersing the above terephthalic acid in the gel
negative electrode prevents or reduces agglomeration of the
particulate negative electrode active material and agglomeration of
a gelling agent. When the negative electrode active material and
the gelling agent are uniformly mixed together in the gel negative
electrode, non-uniform discharge is prevented or reduced, and thus,
discharge performance is improved.
[0016] Furthermore, the gel negative electrode is sufficiently
homogenized, and thus, reliability of the effect of preventing or
reducing flowing of the negative electrode is improved.
[0017] If the terephthalic acid in the negative electrode has an
average particle diameter of less than 25 .mu.m, terephthalic acid
does not sufficiently exhibit an effect of improving dispersibility
of the negative electrode. Furthermore, the negative electrode
active material is likely to be covered with small terephthalic
acid particles, thereby decreasing a surface area (reactive surface
area) of the negative electrode active material that is in contact
with the electrolyte solution. Thus, discharge performance is not
improved.
[0018] On the other hand, if the terephthalic acid in the negative
electrode has an average particle diameter of more than 210 .mu.m,
the negative electrode active material and the gelling agent are
likely to be degraded when they are in contact with the large
terephthalic acid particles, since the large terephthalic acid
particles exhibit a strong rupture force. Furthermore, the
terephthalic acid does not sufficiently exhibit the effect of
improving dispersibility of the negative electrode. Thus, discharge
performance is not improved.
[0019] To further improve the effect of preventing or reducing
flowing of the negative electrode and the effect of improving
discharge performance, the terephthalic acid in the negative
electrode preferably has an average particle diameter of 100 to 210
.mu.m.
[0020] The average particle diameter of the terephthalic acid in
the negative electrode is determined, for example, by the following
method.
[0021] First, the battery is disassembled to obtain the gel
negative electrode. Then, the gel negative electrode is centrifuged
to remove the negative electrode active material from the negative
electrode, and a mixture of the gelling agent and terephthalic acid
particles is obtained. The obtained mixture is dried and thereafter
examined under a light microscope, and 10 terephthalic acid
particles are randomly selected. Then, the particle diameter of
each particle is measured. The two highest measurements and the two
lowest measurements are omitted. The average of the remaining six
measurements is determined as the average particle diameter of the
terephthalic acid in the negative electrode.
[0022] When a gel electrolyte solution (a mixture of the
electrolyte solution and the gelling agent) contained in the
negative electrode contains terephthalic acid having an average
particle diameter of 25 to 210 .mu.m, the gel electrolyte solution
is whitely turbid. At this time, the transmittance of the gel
electrolyte solution is 1% or less.
[0023] The transmittance of the above gel electrolyte solution is
determined by the following method. First, the battery is
disassembled to obtain the negative electrode. Then, the negative
electrode is centrifuged to separate the negative electrode into a
transparent upper layer containing the gel electrolyte solution, a
whitely turbid middle layer containing the gel electrolyte solution
and the terephthalic acid particles, and a lower layer containing
the negative electrode active material. Then, the transmittance of
the middle layer is determined as the transmittance of the gel
electrolyte solution by absorption spectrophotometry.
[0024] The amount of terephthalic acid in the negative electrode is
preferably 0.01 to 0.5 parts by mass relative to 100 parts by mass
of the negative electrode active material. When the amount of
terephthalic acid in the negative electrode is within the above
range, the effect of preventing or reducing flowing of the negative
electrode and the effect of improving discharge performance are
further improved.
[0025] When the amount of terephthalic acid in the negative
electrode is 0.5 parts by mass or less relative to 100 parts by
mass of the negative electrode active material, the negative
electrode has good elasticity and good viscosity. Thus, ease of
pouring the negative electrode into the hollow portion of the
positive electrode is improved.
[0026] As an additive, 0.1 to 1.0 parts by mass of a potassium
halide is preferably contained in the negative electrode relative
to 100 parts by mass of the negative electrode active material.
When the negative electrode contains terephthalic acid having the
specific average particle diameter and the specific amount of
potassium halide in combination, the effect of improving
dispersibility of the negative electrode is further improved, and
thus, discharge performance is further improved, without degrading
the effect of preventing or reducing flowing of the negative
electrode, the effect being exhibited by the terephthalic acid. At
least one of KF and KBr is preferably used as the potassium
halide.
[0027] The amount of potassium halide in the negative electrode is
more preferably 0.1 to 0.5 parts by mass relative to 100 parts by
mass of the negative electrode active material.
[0028] The separator preferably contains 50 to 70 mass % of
polyvinyl alcohol. Polyvinyl alcohol is contained, for example, in
fiber (nonwoven fabric) or a microporous film that forms the
separator.
[0029] When the amount of polyvinyl alcohol in the separator is
within the above range, the strength of the separator is
sufficiently improved. Thus, leakage of the negative electrode to
the positive electrode is further prevented or reduced. In
particular, in an alkaline dry battery having an inside-out
structure, leakage of the negative electrode to the positive
electrode caused by buckling of the separator is further prevented
or reduced.
[0030] When the amount of polyvinyl alcohol in the separator is
within the above range, the liquid-absorption rate of the separator
is sufficiently improved. Thus, high-rate discharge performance is
further improved.
[0031] In an alkaline dry battery having an inside-out structure,
the separator preferably has a thickness of 220 to 390 .mu.m.
[0032] In the present description, the thickness of a separator
refers to the thickness of a separator swollen with an electrolyte
solution. When one sheet is wound a plurality of times or when a
plurality of sheets are layered on each other to form a separator,
the thickness of the separator refers to the total thickness of the
wound sheet (or layered sheets). The total thickness is the sum of
the thickness of the wound sheet or the layered sheets. When one
sheet is wound once or a plurality of times to form a cylindrical
separator, in the case where one end portion of the sheet, at which
winding starts, and the other end portion, at which winding ends,
are layered on each other to improve the strength of the separator,
the thickness of the separator refers to the thickness of a portion
other than the above layered portion.
[0033] When the separator has a thickness of 220 to 390 .mu.m, the
strength of the separator is sufficiently obtained. Thus, leakage
of the negative electrode to the positive electrode caused by
buckling of the separator is further prevented or reduced.
Furthermore, the volume of the hollow portion of the positive
electrode (negative electrode capacity), which is to be filled with
the negative electrode, is sufficiently obtained, and the internal
resistance of the battery is sufficiently decreased. Thus,
discharge performance is further improved. The separator more
preferably has a thickness of 220 to 260 .mu.m.
[0034] Examples of the alkaline dry battery according to an
embodiment of the present invention include cylindrical batteries
and coin batteries.
[0035] Hereinafter, an alkaline dry battery according to the
present embodiments will be described in detail with reference to
the drawing. The present invention is not limited to the following
embodiments. Modifications of the present invention are possible in
a range of the scope in which the advantageous effect of the
present invention is exhibited. Furthermore, combinations with
other embodiments are possible.
[0036] FIG. 1 is a front view of the alkaline dry battery according
to an embodiment of the present invention, with the lateral half of
the view of a cross section of the battery. FIG. 1 is an example of
a hollow cylindrical battery having an inside-out structure. As
shown in FIG. 1, the alkaline dry battery includes a hollow
cylindrical positive electrode 2, a negative electrode 3 disposed
in the hollow portion of the positive electrode 2, a separator 4
disposed therebetween, and an alkaline electrolyte solution (not
shown). These are accommodated in a closed-end cylindrical battery
case 1, which also serves as a positive electrode terminal.
[0037] The positive electrode 2 is in contact with the inner wall
of the battery case 1. The positive electrode 2 contains manganese
dioxide and the alkaline electrolyte solution.
[0038] The hollow portion of the positive electrode 2 is filled
with the gel negative electrode 3 with the separator 4 disposed
therebetween. The negative electrode 3 typically contains the
alkaline electrolyte solution and a gelling agent in addition to
terephthalic acid and a negative electrode active material
containing zinc.
[0039] The separator 4 has a closed-end cylindrical shape and
contains the electrolyte solution. The separator 4 is formed of a
cylindrical separator 4a and a bottom insulator 4b. The separator
4a is disposed along the inner surface of the hollow portion of the
positive electrode 2 and separates the positive electrode 2 and the
negative electrode 3 from each other. Thus, the separator disposed
between the positive electrode and the negative electrode refers to
the cylindrical separator 4a. The bottom insulator 4b is disposed
at the bottom portion of the hollow portion of the positive
electrode 2 and separates the negative electrode 3 and the battery
case 1 from each other.
[0040] The opening portion of the battery case 1 is sealed by a
sealing unit 9. The sealing unit 9 is formed of a gasket 5, a
negative electrode terminal plate 7, which also serves as the
negative electrode terminal, and a negative electrode current
collector 6. The negative electrode current collector 6 is inserted
in the negative electrode 3. The negative electrode current
collector 6 has a nail-like structure including a head portion and
a body portion. The body portion is inserted in a through hole in
the center cylinder of the gasket 5. The head portion of the
negative electrode current collector 6 is welded to a flat portion
in the center portion of the negative electrode terminal plate 7.
The open edge of the battery case 1 is crimped to the flange
portion in the peripheral portion of the negative electrode
terminal plate 7 with the peripheral end portion of the gasket 5
disposed between the open edge and the flange portion. The outer
surface of the battery case 1 is covered with an outer label 8.
[0041] The negative electrode 3 contains terephthalic acid
particles having an average particle diameter of 25 to 210 .mu.m.
This provides appropriate viscosity and elasticity to the negative
electrode 3, and flowing of the negative electrode 3 is
sufficiently prevented or reduced. Thus, even if the battery is
subjected to an impact or vibration when dropped or while being
transported, the negative electrode 3 is unlikely to flow to (be
scattered onto) the gasket 5. Accordingly, leakage of the negative
electrode 3 to the positive electrode 2 that is caused by buckling
of the separator 4a (the end portion near the gasket 5) that occurs
with flowing (scattering) of the negative electrode 3 to the gasket
5 is sufficiently prevented or reduced. As a result, the occurrence
of an internal short circuit caused by the leakage of the negative
electrode 3 to the positive electrode 2 and heat generation in the
battery that occurs with the internal short circuit are prevented.
When the terephthalic acid contained in the negative electrode 3
has an average particle diameter of 25 to 210 .mu.m, good discharge
performance (particularly, high-rate discharge performance) is
obtained.
[0042] Hereinafter, an alkaline dry battery will be described in
detail.
[0043] (Negative Electrode)
[0044] Examples of the negative electrode active material include
zinc and a zinc alloy. From the viewpoint of corrosion resistance,
the zinc alloy may contain at least one selected from a group
consisting of indium, bismuth, and aluminum. In the zinc alloy, the
amount of indium is, for example, 0.01 to 0.1 mass %, and the
amount of bismuth is, for example, 0.003 to 0.02 mass %. The amount
of aluminum in the zinc alloy is, for example, 0.001 to 0.03 mass
%. From the viewpoint of corrosion resistance, the proportion of
elements other than zinc in the zinc alloy is preferably 0.025 to
0.08 mass %.
[0045] The negative electrode active material is typically used in
a powder state. From the viewpoint of diffusivity of the alkaline
electrolyte solution in the negative electrode and ease of pouring
the negative electrode, the negative electrode active material
powder has an average particle diameter (D50) of, for example, 100
to 200 .mu.m, preferably 110 to 160 .mu.m. In the present
description, the term "average particle diameter (D50)" refers to
the median diameter of a volume-based particle diameter
distribution. The average particle diameter is determined, for
example, by using a laser diffraction/scattering particle size
distribution analyzer.
[0046] The negative electrode is obtained, for example, by mixing
negative electrode active material particles containing zinc,
terephthalic acid particles, a gelling agent, and an alkaline
electrolyte solution. A terephthalic acid powder added to the
negative electrode preferably has an average particle diameter
(D50) of 25 to 210 .mu.m, more preferably 100 to 210 .mu.m. In this
case, if the battery is subjected to an impact or vibration when
dropped or while being transported, leakage of the negative
electrode to the positive electrode that is caused by buckling of
the separator that occurs with flowing of the negative electrode is
prevented or reduced, and discharge performance is improved.
[0047] The average particle diameter (D50) P1 of the negative
electrode active material powder used during production of the
negative electrode and the average particle diameter (D50) P2 of
the terephthalic acid powder used during production of the negative
electrode preferably satisfy the following formula:
0.5.ltoreq.P1/P2.ltoreq.5.0
When P1/P2 is within the above range, the effect of preventing or
reducing flowing of the negative electrode and the effect of
improving discharge performance are further improved. The value of
P1/P2 is more preferably 0.6 to 1.3.
[0048] A known gelling agent used in the alkaline dry battery field
is used as the gelling agent without a particular limitation. For
example, a water-absorbent polymer may be used. Examples of such a
gelling agent include polyacrylic acid and sodium polyacrylate.
[0049] The amount of gelling agent added is, for example, 0.5 to
2.5 parts by mass relative to 100 parts by mass of the negative
electrode active material.
[0050] In the negative electrode, for viscosity adjustment or the
like, a surfactant, such as a polyoxyalkylene group-containing
compound or a phosphate, may be used. Among such compounds,
preferable examples include phosphates and alkali metal salts
thereof. From the viewpoint of further uniformly dispersing a
surfactant in the negative electrode, it is preferable that the
surfactant be previously added to an alkaline electrolyte solution
that is used during production of the negative electrode.
[0051] To improve corrosion resistance, a compound containing a
metal, such as indium or bismuth, that has a high hydrogen
overvoltage may be appropriately added to the negative electrode.
To prevent or reduce the growth of dendrites of, for example, zinc,
a trace amount of silicate compound, such as silicic acid or the
potassium salt thereof, may be appropriately added to the negative
electrode.
[0052] (Negative Electrode Current Collector)
[0053] Examples of the material of the negative electrode current
collector to be inserted into the gel negative electrode include
metals and alloys. The negative electrode current collector
preferably contains copper. For example, the negative electrode
current collector may be made of an alloy, such as brass, which
contains copper and zinc. The negative electrode current collector
may be subjected to plating treatment, such as tin plating, if
necessary.
[0054] (Positive Electrode)
[0055] The positive electrode typically contains an electrically
conductive agent and an alkaline electrolyte solution in addition
to manganese dioxide that is a positive electrode active material.
The positive electrode may further contain a binder, if
necessary.
[0056] It is preferable that electrolytic manganese dioxide be used
as the manganese dioxide. The crystal structures of manganese
dioxide include an .alpha.-type, .beta.-type, .gamma.-type,
.delta.-type, .epsilon.-type, .eta.-type, .lamda.-type, and
ramsdellite-type structures.
[0057] Manganese dioxide is used in a powder state. From the
viewpoint that diffusivity of the electrolyte solution in the
positive electrode and ease of pouring the positive electrode are
easily obtained, the average particle diameter (D50) of manganese
dioxide is, for example, 25 to 60 .mu.m.
[0058] From the viewpoint of formability and prevention or
reduction of positive electrode expansion, the BET specific surface
area of manganese dioxide may be, for example, within the range of
20 to 50 m.sup.2/g. The BET specific surface area is determined by
measuring and calculating a surface area by using the BET formula,
which is the formula based on the multi-molecular layer adsorption
theory. The BET specific surface area may be measured, for example,
by using a specific surface area analyzer using a nitrogen
adsorption method.
[0059] Examples of the electrically conductive agent include
electrically conductive carbon materials, such as graphite, in
addition to carbon black, such as acetylene black. For example,
natural graphite or synthetic graphite can be used as the graphite.
The electrically conductive agent may be fiber but is preferably
powder. The electrically conductive agent has an average particle
diameter (D50) of, for example, 3 to 20 .mu.m.
[0060] The amount of electrically conductive agent in the positive
electrode is, for example, 3 to 10 parts by mass and preferably 5
to 9 parts by mass relative to 100 parts by mass of manganese
dioxide.
[0061] The positive electrode is obtained, for example, by
pressure-molding a positive electrode mixture containing a positive
electrode active material, an electrically conductive agent, an
alkaline electrolyte solution, and, if necessary, a binder into a
pellet. The positive electrode mixture may be pressure-molded into
a pellet after being made into flakes or granules and, if
necessary, classified.
[0062] The pellet is accommodated in a battery case, and
thereafter, a secondary pressure is applied to the pellet, by using
a predetermined instrument, such that the pellet adheres to the
inner wall of the battery case.
[0063] (Separator)
[0064] Examples of the material of the separator include cellulose
and polyvinyl alcohol. The separator may be nonwoven fabric in
which the main constituent is fiber of the above material or a
microporous film, such as a cellophane film or a polyolefin-based
film. Nonwoven fabric and a microporous film may be used in
combination with each other.
[0065] Nonwoven fabric is preferably used as the separator. From
the viewpoint of improving the separator strength, the nonwoven
fabric preferably contains polyvinyl alcohol fiber. Such nonwoven
fabric is obtained, for example, by mixing together polyvinyl
alcohol fiber and another fiber other than polyvinyl alcohol fiber.
Specific examples include nonwoven fabric in which cellulose fiber
and polyvinyl alcohol fiber are mixed together as the main
constituents and nonwoven fabric in which rayon fiber and polyvinyl
alcohol fiber are mixed together as the main constituents. From the
viewpoint of preventing or reducing leakage of the negative
electrode to the positive electrode that is caused by buckling of
the separator and from the viewpoint of improving discharge
performance, the amount of polyvinyl alcohol fiber in the nonwoven
fabric is preferably 50 to 70 mass %.
[0066] In FIG. 1, the closed-end cylindrical separator 4 is formed
of the cylindrical separator 4a and the bottom insulator 4b. The
closed-end cylindrical separator is not limited to such a structure
and may be a known-shape separator used in the alkaline dry battery
field. The separator may be formed of one sheet or a plurality of
sheets layered on each other if the sheet used as the separator is
thin. The cylindrical separator may be formed of a thin sheet wound
a plurality of times.
[0067] (Alkaline Electrolyte Solution)
[0068] The alkaline electrolyte solution is contained in the
positive electrode, the negative electrode, and the separator. For
example, an alkaline aqueous solution containing potassium
hydroxide is used as the alkaline electrolyte solution. The
concentration of potassium hydroxide in the alkaline electrolyte
solution is preferably 30 to 50 mass %. The alkaline aqueous
solution may further contain zinc oxide. The concentration of zinc
oxide in the alkaline electrolyte solution is, for example, 1 to 5
mass %.
[0069] (Battery Case) [0070] For example, a closed-end cylindrical
metal case is used as the battery case. For the metal case, a
nickel-plated steel sheet may be used. To improve adhesion between
the positive electrode and the battery case, a battery case
obtained by covering the inner surface of a metal case with a
carbon coating is preferably used.
EXAMPLES
[0071] Hereinafter, the present invention will be specifically
described in accordance with Examples and Comparative Examples. The
present invention is not limited to the following Examples.
Example 1
[0072] The AA-size cylindrical alkaline dry battery (LR6)
illustrated in FIG. 1 was produced in accordance with the following
steps (1) to (3).
[0073] (1) Production of Positive Electrode
[0074] A graphite powder (average particle diameter (D50) 8 .mu.m)
that was the electrically conductive agent was added to an
electrolytic manganese dioxide powder (average particle diameter
(D50) 35 .mu.m) that was the positive electrode active material to
obtain a mixture. The mass ratio of the electrolytic manganese
dioxide powder to the graphite powder was set to 92.4:7.6. The
electrolytic manganese dioxide powder had a specific surface area
of 41 m.sup.2/g. After an electrolyte solution was added to the
mixture and stirred well, compression-molding was performed to make
the resulting mixture into flakes to obtain a positive electrode
mixture. The mass ratio of the mixture to the electrolyte solution
was set to 100:1.5. An alkaline aqueous solution containing
potassium hydroxide (concentration, 35 mass %) and zinc oxide
(concentration, 2 mass %) was used as the electrolyte solution.
[0075] The flake positive electrode mixture was pulverized into
granules, and the granules were classified by using a sieve. Eleven
grams of 10 to 100 mesh granules were pressure-molded to produce
two positive electrode pellets having a predetermined hollow
cylindrical shape with an outer diameter of 13.65 mm.
[0076] (2) Production of Negative Electrode
[0077] A zinc alloy powder (average particle diameter (D50) 130
.mu.m) that was the negative electrode active material, a
terephthalic acid powder (average particle diameter (D50) 26
.mu.m), the above electrolyte solution, and a gelling agent were
mixed together to obtain the gel negative electrode 3. A zinc alloy
containing 0.02 mass % of indium, 0.01 mass % of bismuth, and 0.005
mass % of aluminum was used as the zinc alloy. A mixture of
crosslinked and branched polyacrylic acid and highly-crosslinked
chain sodium polyacrylate was used as the gelling agent. The
negative electrode active material/electrolyte solution/gelling
agent mass ratio was set to 100:50:1. Relative to 100 parts by mass
of the negative electrode active material, 0.2 parts by mass of
terephthalic acid was used.
[0078] (3) Assembly of Alkaline Battery
[0079] To obtain the battery case 1, varniphite, manufactured by
Nippon Graphite Industries, Co., Ltd., was applied to the inner
surface of a closed-end cylindrical battery case (outer diameter
13.80 mm, wall thickness of the cylindrical portion 0.15 mm, height
50.3 mm) made of a nickel-plated steel sheet to form a carbon
coating having a thickness of about 10 .mu.m. After the two
positive electrode pellets were inserted into the battery case 1 so
as to be longitudinally stacked, pressure was applied to form the
positive electrode 2, which adheres to the inner wall of the
battery case 1. After the closed-end cylindrical separator 4 was
disposed inside the positive electrode 2, the above electrolyte
solution was injected to impregnate the separator 4 therewith. The
electrolyte solution was left for a predetermined time in this
state to permeate from the separator 4 to the positive electrode 2.
Then, the inside of the separator 4 was filled with 6 g of the gel
negative electrode 3.
[0080] The separator 4 was formed of the cylindrical separator 4a
and the bottom insulator 4b. Nonwoven fabric sheets (basis weight
28 g/m.sup.2) in which rayon fiber and polyvinyl alcohol fiber were
mixed together as the main constituents at a mass ratio of 1:1 were
used as the cylindrical separator 4a and the bottom insulator 4b.
The nonwoven fabric sheet used as the bottom insulator 4b had a
thickness of 0.27 mm.
[0081] The separator 4a (the thickness before becoming swollen, 206
.mu.m) was formed of a nonwoven fabric sheet having a thickness of
103 .mu.m wound twice. At this time, a portion where one end
portion of the nonwoven fabric sheet, at which winding started, and
the other end portion of the nonwoven fabric sheet, at which
winding ended, were layered on each other was provided. In a cross
section perpendicular to the axial direction (X direction in FIG.
1) of the positive electrode of the separator, the length of the
layered portion was set to 3 mm.
[0082] The negative electrode current collector 6 was obtained by
pressing typical brass (Cu content: about 65 mass %, Zn content:
about 35 mass %) into a nail shape, and thereafter, the surface was
plated with tin. The diameter of the body portion of the negative
electrode current collector 6 was set to 1.15 mm. The head portion
of the negative electrode current collector 6 was electrically
welded to the negative electrode terminal plate 7 made of a
nickel-plated steel sheet. Then, the body portion of the negative
electrode current collector 6 was inserted with pressure into the
through hole in the center of the gasket 5, in which polyamide 6
and polyamide 12 are contained as the main constituents. As
described above, the sealing unit 9 formed of the gasket 5, the
negative electrode terminal plate 7, and the negative electrode
current collector 6 was produced.
[0083] The sealing unit 9 was then disposed at the opening of the
battery case 1. At this time, the body portion of the negative
electrode current collector 6 was inserted into the negative
electrode 3. The open edge of the battery case 1 was crimped to the
peripheral portion of the negative electrode terminal plate 7 with
the gasket 5 disposed therebetween to seal the opening of the
battery case 1. The outer surface of the battery case 1 was covered
with the outer label 8. As described above, the alkaline dry
battery was produced.
Examples 2
[0084] An alkaline dry battery was produced in the same manner as
in Example 1, except that the average particle diameter of the
terephthalic acid in the negative electrode was changed to the
value in Table 1.
Comparative Example 1
[0085] An alkaline dry battery was produced in the same manner as
in Example 1, except that terephthalic acid was not used during
production of the negative electrode.
Comparative Examples 2 to 4
[0086] An alkaline dry battery was produced in the same manner as
in Example 1, except that the average particle diameter of the
terephthalic acid in the negative electrode was changed to the
value in Table 1.
Comparative Example 5
[0087] An alkaline dry battery was produced in the same manner as
in Example 1, except that a phthalic acid (ortho isomer) powder was
used instead of the terephthalic acid (para isomer) powder during
production of the negative electrode.
Comparative Example 6
[0088] An alkaline dry battery was produced in the same manner as
in Example 1, except that an isophthalic acid (meta isomer) powder
was used instead of the terephthalic acid (para isomer) powder
during production of the negative electrode.
[0089] [Evaluation]
[0090] The obtained alkaline dry batteries were evaluated as
follows.
[0091] (i) Safety Evaluation
[0092] Twenty batteries in each of Examples and Comparative
Examples were provided. Two batteries in each of examples were
disposed in series and fixed to each other by using a tape. The two
batteries were dropped from a height of 1 m to a concrete floor
with the negative electrode (the negative electrode terminal plate
7 in FIG. 1) facing downward. The step of dropping was repeated
three times. At this time, the number of batteries generating heat
to have a temperature of 40.degree. C. or higher was counted, and
the percentage of batteries generating heat was calculated.
[0093] (ii) Evaluation of High-Rate Pulse Discharge Performance
[0094] Under an environment of 20.+-.2.degree. C., a pulse
discharge in which a discharge at 1.5 W for two seconds and a
discharge at 0.65 W for 28 seconds were alternately repeated 10
times was performed, and the pulse discharge was followed by a
pause of 55 minutes. This step was repeatedly performed until the
closed-circuit voltage of the battery reached 1.05 V. At this time,
the time that elapsed until the closed-circuit voltage of the
battery reached 1.05 V was measured and expressed as an index
relative to the discharge time in Comparative Example 1, when the
discharge time in Comparative Example 1 was assumed to be 100.
[0095] (iii) Measurement of Average Particle Diameter of
Terephthalic Acid in Negative Electrode
[0096] After the battery was disassembled to obtain the gel
negative electrode, the gel negative electrode was centrifuged to
remove the negative electrode active material from the negative
electrode, and a mixture of a gelling agent and terephthalic acid
particles was obtained. The obtained mixture was dried and
thereafter examined under a light microscope, and 10 terephthalic
acid particles were randomly selected. Then, the particle diameter
of each particle was measured. The two highest measurements and two
lowest measurements were removed. The average of the remaining six
measurements was determined as the average particle diameter of the
terephthalic acid in the negative electrode.
[0097] (iv) Measurement of Thickness of Separator (After Becoming
Swollen)
[0098] The image of the cross section (a cross section
perpendicular to the X direction in FIG. 1) at a point separated by
20 mm in the axial direction (X direction in FIG. 1) of the battery
from the surface of the positive electrode terminal was examined by
using a CT scanner to measure the distance between the positive
electrode and the negative electrode (length in the radial
direction). The distance was regarded as the thickness of the
separator 4a (swollen with the electrolyte solution). First,
measurement was performed at an arbitrary point (not in a portion
where one end portion, at which winding started, and the other end
portion, at which winding ended, were layered on each other) in a
portion where the cylindrical separator 4a was disposed between the
positive electrode and the negative electrode. The measurement was
performed in the same manner at points (other three points not in a
portion where one end portion, at which winding started, and the
other end portion, at which winding ended, were layered on each
other) that were each obtained when the battery was rotated at
90.degree. at a time around the axis of the battery. Among the four
measurements, the average of two measurements other than the
highest value and the lowest value was determined.
[0099] Evaluation results are summarized in Table 1.
TABLE-US-00001 TABLE 1 Negative electrode Average Evaluation
particle Amount of Percentage of diameter of terephthalic batteries
High-rate terephthalic acid generating discharge Acid (parts by
White heat performance (.mu.m) mass) turbidity (%) (index)
Comparative -- 0 absent 50 100 Example 1 Comparative 2 0.2 absent
50 100 Example 2 Comparative 24 0.2 present 0 100 Example 3 Example
1 26 0.2 present 0 103 Example 2 100 0.2 present 0 106 Example 3
130 0.2 present 0 116 Example 4 204 0.2 present 0 106 Comparative
217 0.2 present 0 100 Example 4 Comparative (dissolved) 0.2 absent
100 96 Example 5 (phthalic acid) Comparative (dissolved) 0.2 absent
100 92 Example 6 (isophthalic acid)
[0100] The average particle diameter of the terephthalic acid in
the negative electrode was about 26 .mu.m in Example 1, about 100
.mu.m in Example 2, about 130 .mu.m in Example 3, and about 204
.mu.m in Example 4. The average particle diameter of the
terephthalic acid in the negative electrode was about 2 .mu.m in
Comparative Example 2, about 24 .mu.m in Comparative Example 3, and
about 217 .mu.m in Comparative Example 4.
[0101] The thickness of the separator (after becoming swollen) in
Examples 1 to 4 and Comparative Examples 1 to 6 was about 260
.mu.m.
[0102] In Examples 1 to 4 and Comparative Examples 3 and 4, the
negative electrode contains terephthalic acid particles having an
average particle diameter of more than 20 .mu.m. Thus, the negative
electrode was whitely turbid. In Comparative Examples 5 and 6,
during production of the negative electrode, phthalic acid or
isophthalic acid dissolved in the negative electrode. Thus, the
negative electrode was not whitely turbid and was colorless. In
Comparative Example 2, terephthalic acid particles contained in the
negative electrode were very small. Thus, the negative electrode
was not whitely turbid.
[0103] In Examples 1 to 4, the negative electrode contains the
terephthalic acid having the specific average particle diameter,
thereby preventing or reducing flowing of the negative electrode.
Thus, there were no batteries generating heat.
[0104] In Examples 1 to 4, high-rate discharge performance was
improved. The reason is probably that the negative electrode
contains the terephthalic acid having the specific average particle
diameter and thus, the negative electrode active material and the
gelling agent were uniformly mixed together in the negative
electrode, thereby preventing or reducing non-uniform discharge. In
Examples 2 to 4, in which the terephthalic acid in the negative
electrode had an average particle diameter of 100 to 210 .mu.m,
excellent high-rate discharge performance was obtained.
[0105] In Comparative Example 1, the negative electrode did not
contain the terephthalic acid having the specific average particle
diameter, and thus, flowing of the negative electrode was neither
prevented nor reduced. Accordingly, there were batteries generating
heat. Furthermore, in Comparative Example 1, the negative electrode
did not contain the terephthalic acid having the specific average
particle diameter, and thus, discharge performance was not
improved.
[0106] In Comparative Example 2, terephthalic acid particles were
very small. Thus, the effect of preventing or reducing flowing of
the negative electrode was not exhibited, and there were batteries
generating heat.
[0107] In Comparative Examples 2 and 3, discharge performance was
not improved. The reason is probably that the terephthalic acid
particles were small and thus, the effect of improving
dispersibility of the negative electrode was not sufficiently
exhibited. The reason is also probably that the negative electrode
active material was largely covered by the small terephthalic acid
particles, thereby decreasing a surface area (reactive surface
area) of the negative electrode active material that was in contact
with the electrolyte solution.
[0108] In Comparative Example 4, the negative electrode active
material and the gelling agent were degraded by contact with large
terephthalic acid particles. Thus, the discharge performance was
not improved.
[0109] In Comparative Examples 5 and 6, in which phthalic acid or
isophthalic acid was added to the negative electrode, flowing of
the negative electrode was neither prevented nor reduced. Thus,
there were batteries generating heat. Furthermore, in Comparative
Examples 5 and 6, discharge performance was lower than that in
Comparative Example 1.
[0110] Here, evaluation results of an anti-corrosion effect of
terephthalic acid on the negative electrode active material will be
described. A battery in Comparative Example 1 to which terephthalic
acid was not added, a battery in Comparative Example 2 to which
terephthalic acid having an average particle diameter of 2 .mu.m
was added, and a battery in Example 2 to which terephthalic acid
having an average particle diameter of 100 .mu.m was added were
stored for 28 days at 60.degree. C. Then, the batteries were opened
by a water displacement method, and the amount of gas collected was
measured. The amount of gas was 0.65 ml in the battery in
Comparative Example 1, 0.55 ml in the battery in Comparative
Example 2, and 0.80 ml in the battery in Example 2. Thus, it has
been found that large terephthalic acid particles having an average
particle diameter of 100 .mu.m improve discharge performance and
safety, but do not have an anti-corrosion effect.
Examples 5 to 8
[0111] An alkaline dry battery was produced in the same manner as
in Example 3, except that the amount of terephthalic acid (relative
to 100 parts by mass of the negative electrode active material) was
the value in Table 2 during production of the negative electrode,
and evaluated.
[0112] Evaluation results are summarized in Table 2.
TABLE-US-00002 TABLE 2 Negative electrode Average Evaluation
particle Amount of Percentage of diameter of terephthalic batteries
High-rate terephthalic acid generating discharge Acid (parts by
heat performance (.mu.m) mass) (%) (index) Example 5 130 0.005 0
101 Example 6 130 0.01 0 109 Example 3 130 0.2 0 116 Example 7 130
0.5 0 109 Example 8 130 1.0 0 101
[0113] In Examples 3, 6, and 7, in which the amount of terephthalic
acid was 0.01 to 0.5 parts by mass relative to 100 parts by mass of
the negative electrode active material, there were no batteries
generating heat. Furthermore, in Examples 3, 6, and 7, high-rate
discharge performance was greatly improved by about 10% or
more.
Examples 9 and 10
[0114] An alkaline dry battery was produced in the same manner as
in Example 3, except that the amount of polyvinyl alcohol in the
separator (the amount of polyvinyl alcohol fiber in the nonwoven
fabric) is the value in Table 3 during production of the separator,
and evaluated.
[0115] Evaluation results are summarized in Table 3.
TABLE-US-00003 TABLE 3 Negative electrode Average Evaluation
particle Amount of Separator Percentage diameter of terephthalic
Amount of of batteries High-rate terephthalic acid polyvinyl
generating discharge Acid (parts by alcohol heat performance
(.mu.m) mass) (mass %) (%) (index) Example 9 130 0.2 50 0 109
Example 3 130 0.2 65 0 116 Example 10 130 0.2 70 0 110
[0116] In Examples 3, 9, and 10, in which the amount of polyvinyl
alcohol in the separator was 50 to 70 mass %, there were no
batteries generating heat. In Examples 3, 9, and 10, high-rate
discharge performance was greatly improved by about 10% or
more.
Example 11
[0117] An alkaline dry battery was produced in the same manner as
in Example 3, except that 0.1 parts by mass of KF was added
relative to 100 parts by mass of the negative electrode active
material during production of the negative electrode, and
evaluated.
Examples 12 to 14
[0118] An alkaline dry battery was produced in the same manner as
in Example 3, except that 0.1, 0.5, or 1.0 parts by mass of KBr was
added relative to 100 parts by mass of the negative electrode
active material during production of the negative electrode, and
evaluated.
[0119] Evaluation results are summarized in Table 4.
TABLE-US-00004 TABLE 4 Negative electrode Evaluation Average
particle Percentage High-rate diameter of Amount of Amount of of
batteries discharge terephthalic acid terephthalic acid co-additive
generating heat performance (.mu.m) (parts by mass) Co-additive
(parts by mass) (%) (index) Example 3 130 0.2 -- -- 0 116 Example
11 130 0.2 KF 0.1 0 121 Example 12 130 0.2 KBr 0.1 0 122 Example 13
130 0.2 KBr 0.5 0 123 Example 14 130 0.2 KBr 1.0 0 116
[0120] In Examples 11 to 14, there were no batteries generating
heat, and high-rate discharge performance was improved. In
particular, in Examples 11 to 13, high-rate discharge performance
was greatly improved by about 20% or more.
INDUSTRIAL APPLICABILITY
[0121] According to an embodiment of the present invention, the
battery can be used in various devices using dry batteries as a
power source. Suitable examples of the device include portable
audio devices, electronic games, lights, and toys.
REFERENCE SIGNS LIST
[0122] 1 battery case
[0123] 2 positive electrode
[0124] 3 negative electrode
[0125] 4 closed-end cylindrical separator
[0126] 4a cylindrical separator
[0127] 4b bottom insulator
[0128] 5 gasket
[0129] 6 negative electrode current collector
[0130] 7 negative electrode terminal plate
[0131] 8 outer label
[0132] 9 sealing unit
* * * * *